The present invention generally relates to chemical sensors for monitoring, detecting and/or measuring parameters at locations remote from detection instrumentation. More particularly, the invention relates to chemical sensor components that are positioned at a remote or distal portion of an optical fiber waveguide, which chemical sensor components incorporate a charged indicator component electrostatically coupled to oppositely charged ion exchange resin material dispersed within a charged hydrogel matrix membrane.
Chemical sensors secured to the distal end of optical fibers are generally known to be useful for a wide variety of purposes, especially in the areas of medicine, scientific research, industrial applications and other situations where it may be desired to detect and/or measure the concentration of a parameter at a remote location without requiring electrical communication with the remote location. Descriptive materials which describe the structure, properties, functions and operational details of fiber optic chemical sensors include U.S. Pat. Nos. 4,577,109 and 4,785,814, as well as Sietz, "Chemical Sensors Based on Fiber Optics", Analytical Chemistry, Vol. 56, No. 1, January, 1984, each of which is incorporated by reference hereinto.
Publications such as these generally illustrate that it is known to incorporate a chemical sensor into a fiber optic waveguide in a manner such that the chemical sensor will interact with the analyte. This interaction results in a change in optical properties, typically a change in color or color intensity, which is transmitted through the fiber optic waveguide and to a suitable detection device. In these types of systems, it is possible to detect particularly minute changes in the parameter being monitored in order to thereby provide especially sensitive remote monitoring capabilities.
Chemical sensor compositions that are incorporated at the distal end of these types of fiber optic sensors are often configured as membranes that are secured at the distal tip end of the waveguide device or optrode. Specific examples of membranes for optrodes are found in U.S. Pat. No. 4,272,485, which proposes a variety of membrane mobile carrier substances for transporting particles within the membrane. In this patent, a carrier is described which may be either charged or uncharged that takes up particles in the solution being monitored and transports them through the membrane and into the optrode. The carrier is characterized as being mobile within the membrane and as transporting the particles through the membrane. Highly selective indicators, as well as a broadened range of measurement applicability, are said to be achieved by this transport carrier approach.
Optrodes having chemical sensors such as those discussed in these publications are useful in monitoring or measuring pH, oxygen concentrations, carbon dioxide concentrations and the like. Cation concentrations can also be detected, such as potassium, sodium, calcium ions, as well as metal ions. Often, these types of devices are used in medical applications for in vivo monitoring of biological fluids. Other areas in which fiber optic chemical sensors may be useful include the monitoring of chemical conditions during industrial processes, such as taking industrial biological measurements. An example of the specific industrial type of application includes the use of optical fibers for measuring conditions within submerged wells and the like.
It has been determined that, by proceeding in accordance with the present invention, it is possible to utilize opposite charges of interacting components in order to substantially irreversibly bind the color indicator within a matrix that can function as a membrane which adheres to a fiber optic in order to provide an optrode arrangement that will be useful in monitoring various parameters of the types discussed herein. Ion exchange resin powders having the indicator material electrostatically coupled thereto are dispersed within a charged hydrogel membrane material carrying an overall charge that is opposite to the charge presented by the ion exchange resin powder. The present invention preferably includes the use of a water-insoluble cationic ion exchange resin bound to an anionic color indicator, which resin and indicator combination is dispersed in an anionic hydrogel matrix that adheres to a fiber optic waveguide in order to thereby provide an optrode assembly. When desired, the various materials can be selected in order to provide a fiber optic waveguide and optrode assembly that is biocompatible.
It is a general object of the present invention to provide an improved fiber optic chemical sensor.
Another object of the present invention is to provide an improved fiber optic chemical sensor that utilizes ion exchange resin technology whereby opposite charges can be advantageously utilized to form a membrane or matrix that is especially durable while still presenting an optrode that is colorimetrically responsive to desired parameters or components.
Another object of this invention is to provide an improved fiber optic chemical sensor that is biocompatible and very non-thrombogenic.
Another object of the present invention is to provide an improved fiber optic chemical sensor which simplifies retention of the dye component therewithin by ionically retarding leaching thereof.
Another object of this invention is to provide an improved fiber optic chemical sensor that presents an anionic surface which reduces the likelihood that components within the bloodstream or the like would interfere with the fluorescent signal developed by the sensor.
These and other objects, features and advantages of this invention will be clearly understood through a consideration of the following detailed description.